Midspan electrical conductor spacer

ABSTRACT

A midspan spacer for maintaining adjacent high voltage conductors in spaced relationship includes an elongated, relatively lightweight spacer unit of insulating material, a conductor clamp at either end of the unit, and an insulator having high flash over-resistance characteristics adjacent each of the clamps. The spacer unit is characterized by a high compressive strength in relationship to its weight to withstand the substantial forces exerted thereon when the conductors tend to move relative to each other. All of the components of the spacer are held together by a bonding agent, and means is provided to load each of the bonds in compression, thereby utilizing the full load-bearing capacity of the bonding agent.

United States Patent [72] inventor 211 Appl. No. [22] Filed [45] Patented [73] Assignee [54] MIDSPAN ELECTRICAL CONDUCTOR SPACER 14 Claims, 6 Drawing Figs.

[52] U.S. Cl 174/146, 174/169, l74/l78,l74/l82 [5 1] Int. Cl. ..ll0lb i i/1 6, H0lb17/32QH02g 7/12 [50] Field of Search 174/42,

[56] v 1 References Cited UNITED STATES PATENTS 1,502,829 7/1924 Kempton 174/ 140( l) X 3,198,878 8/1965 Kaczerginski 174/150x 3,468,740 9/1969 Kaczerginski l74/l78X FOREIGN PATENTS 134,39 9/1966 U.S.S.R. 174/146 add.88,768 2/1967 France l74/l78 Primary Examiner- Laramie E. Askin Attorney-Schmidt, Johnson, l-lovey, Williams and Chase ABSTRACT: A midspan spacer for maintaining adjacent high voltage conductors in spaced relationship includes an elongated, relatively lightweight spacer unit of insulating material, a conductor clamp at either end of the unit, and an insulator having high flash over-resistance characteristics adjacent each of the clamps. The spacer unit is characterized by a high compressive strength in relationship to its weight to withstand the substantial forces exerted thereon when the conductors tend to move relative to each other. All of the components of the spacer are held together by a bonding agent, and means is provided to load each of the bonds in compression, thereby utiliz ing the full load-bearing capacity of the bonding agent.

PATENTEU JUN1 51971 SHEU 1 BF 2 QN E m I 6 am ww S l 0 \Y Q v 1 2 wmmw V SQ 5 W Wm em w u VVILx- I,

Paul E. Lewis BY I a J "WM I (")ALM KIT TORNCYS.

PATENTEU Jun] 5 I97! SHEET 2 OF 2 W0. W8 JAN MI R W 5 A w i am each case.

Wind-induced vibration is a persistent operating hazard of overhead transmission lines, and the most dangerous category of wind-induced line movements has traditionally been designated galloping. Although galloping conductors are not encountered during normal weather and atmospheric conditions, the buildup of ice on the lee side of a conductor can cause a crude airfoil which, in conjunction with the torsional response of the conductor, can produce a varied assortment of violent wave motions. The introduction of bundle conductor systems in recent years has caused renewed interested in attempting to control galloping conductors, since bundle conductor systems have been observed vibrating in large amplitudes when no ice was present.

Attempts to provide a spacer for spanning the substantial distance between different phase conductors of a multiple phase transmission line has met with little success. The problem which has heretofore not been overcome is meeting the rather substantial insulator requirements necessary to prevent flashover between phases, while keeping the spacer sufficiently lightweight so as not to interfere with the drape of the lines. The fact that a midspan spacer must be relatively lightweight has also prevented the construction of a unit of sufficient strength to withstand the substantial forces exerted thereon when adjacent conductors tend to move relative to one another. It has also been found that it is desirable to construct a midspan spacer in a rigid assembly, avoiding any moving parts. This is necessary to reduce arcing and resulting radio interference which can occur, especially when moving parts become contaminated. More importantly, numerous in vestigations of galloping conductors have shown that torsional rotation of a conductor is an essential element of galloping movement. Only with a completely rigid structure can such torsional forces be completely eliminated.

It is, therefore, an object of the present invention to provide a spacer for insertion at midspan of a multiple phase high voltage transmission line which, because of its light weight, does not adversely affect the drape of the line.

It is another object of the present invention to provide a spacer for insertion at midspan of a high voltage transmission line which, because of its insulative properties can be placed between different phases of a multiple phase line without danger of flashover between lines.

Still another object of the invention is'to provide a high voltage transmission line spacer having sufficient strength vto withstand the substantial forces which tend to move adjacent lines relative to each other.

' spacer as described in foregoing objects wherein a frustoconical fitting loads the bonding agent in compression, thereby utilizing the maximum strength of the bonding agent.

Still another important object of the invention is to provide a midspan spacer which, because of its completely rigid structure, does not result in increased radio interference along a transmission line.

A very important object of this invention is also to provide a midspan spacer which, because of its completely rigid structure, is effective in eliminating the torsional movements which are associated with galloping conductors.

It is also an object of this invention to provide a midspan spacer of rigid construction as described in the foregoing objects wherein the component parts of the spacer can be individually replaced for economical maintenance.

In the drawings:

FIG. 1 is a front elevational view of a midspan spacer with one of the insulators, one of the connecting ferrules and portions of one of the conductor clamps being shown in cross section;

FIG. 2 is a front elevational view of an alternative embodiment of the midspan spacer with the two insulators and pertions of the connections and protective jacket around the spacer unit being shown in cross section;

FIG. 3 is a front elevational view of the midspan spacer shown in FIG. 1 illustrating a different form of conductor clamp which may be utilized therewith;

FIG. 4 is a front elevational view of an alternative embodiment of the midspan spacer with one of the insulators and certain other portions being shown in cross section;

FIG. 5 is a front elevational view of still another alternative embodiment of the midspan spacer with the insulators at either end of the spacer unit, the conductor clamps, the protective jacket over the spacer unit, and other portions of the apparatus being shown in cross section; and

FIG. 6 is a front elevational view of yet another alternative embodiment of the midspan spacer with major portions of the same being shown in cross section for purposes of illustration.

Referring initially to the preferred embodiment of the spacer apparatus which is shown in FIG. 2 of the drawings and designated generally by the numeral 10, the apparatus 10 includes an elongated insulator assembly 12 which has a pair of insulators l4 and 16 secured to opposite ends thereof, and a pair of conductor clamps l8 and 20 adjacent each of the insulators l4 and 16 respectively. The insulator assembly 12 includes an elongated, relatively lightweight spacer unit 22 which is preferably constructed from a fiberglass reinforced resinous material and connecting portions 24 and 26 which connect the insulators 14 and 16 respectively to the spacer unit 22. Metal ferrules 28 and 30, each of which has opposed openings therein are secured to the spacer unit 22 by an appropriate bonding .agent. Each of the connecting portions 24 and 26 is provided with a threaded stud 32 and 34 respectively which is received within one of the openings of the ferrules 28 and 30 respectively. The spacerunit 22 is provided with a protective jacket 36 ofinsulating material, such as an epoxy resin, which is disposed in surrounding relationship to the unit 22 and frictionally engages the same over substantially the entire length thereof. If is also to be noted that the jacket 36 abuts the respective ferrules 28 and 30.

Each of the insulators l4 and 16 comprises an annular body having an uninterrupted curvilinear first surface 38 and 40 respectively, and a second surface 42 and 44 respectively comprised of a plurality of interconnected annular ridges. Each of the insulators 14 and 16, which is preferably constructed from a material such as porcelain having high flashover resistance characteristics, is configured to present a cap 46 and 48 on the side of its curvilinear surface 38 and 40, respectively, and a cavity 50 and 51 opposite each of the caps 46 and 48 respectively.

It is to be noted that the insulator 14 is disposed with its cap 46 extending away from the insulator assembly 12, while the other insulator 16 is disposed with its cap 48 extending toward the assembly 12. With this arrangement of the insulators l4 and 16, the connecting portion 24 is configured to present a frustoconical tongue 52 which is disposed within the cavity 50. A suitable bonding agent 54 is disposed within the cavity 50 and interconnects the insulator 14 with the tongue 52. The connecting portion 26 is provided with a depending skirt 56 which terminates in a frustoconical lip. The cap 48 is covered with a layer of the bonding agent 54 and the skirt 56 is disposed in circumscribing relationship to the cap 48 and the bonding agent 54 thereon.

The U-sh'aped saddle-type conductor clamp 18 is provided with a depending skirt 58 which, like the skirt 56, terminates in a frustoconical lip and circumscribes the cap 46 with a layer of the bonding agent 54 securing the skirt 58 to the cap 46. The conductor clamp20, which is generally of the same type as the conductor clamp 18, is provided within the cavity 51. A layer of the bonding agent 54 is also placed within cavity 51 to join the tongue 60 to the cap 48.

It is to be understood that portions of the conductor clamps l8 and have been omitted from FIG. 2 for purposes of illustration only, although the omitted portions are shown and described in conjunction with the embodiment of FIGS. 1 and 3. When the conductor clamps 18 and 20 are secured to two adjacent phases of a multiple phase transmission line with the insulator assembly 12 substantially spanning the normal distance between the conductors, the two phases will be maintained in their normal predetermined spaced relationship even under conditions which would normally produce galloping conductors.

A very desirable feature in the construction of the apparatus 10 is the provision of frustoconical bond-engaging means for each of the bonding layers 54. It is to be emphasized that a suitable parting agent, for example silicone or petrolatum, is normally placed on the metal component, such as tongue 52 or skirt 58, with which the bonding layer 54 comes in contact to prevent the latter from adhering to two surfaces. This eliminates the possibility of shear forces acting on the bonding layer and, by virtue of the frustoconical portions, the bonds are loaded in compression when the two conductors tend to move away from each other, thereby utilizing the compression strength of the bonding agent which is normally considerably greater than its tensile strength. It is also important for the spacer unit 22 to be constructed from a material having a high compressive strength in relationship to the weight thereof in order for the unit to withstand the substantial compressive forces which are exerted thereon when two phases tend to move toward each other. The protective jacket 36 which surrounds the spacer 22, serves as a shield to protect the spacer from atmospheric contaminants which would detract from its insulative properties. If the jacket 36 becomes excessively contaminated, the spacer 22 can be replaced at a relatively small cost. The disposition of the jacket 36 in abutting relationship to the ferrules 28 and 30 also helps to eliminate corona effects at the edges of the ferrules, since these components are usually constructed from a conductive material.

Referring additionally to FIGS. 1 and 3, an alternative embodiment of the apparatus 10 is designated generally by the numeral 62 and includes an elongated insulator assembly 12 of the type previously described, having a spacer unit 22, con necting portions 24 and 26 and ferrules 28 and 30 which are assembled together in the same manner as previously described for the preferred embodiment. A pair of conductor clamps 63 in FIG. 1, and 63a in FIG. 3, are joined to the insulators l4 and 16 respectively by connecting legs 64 and 66 respectively. Each of the connecting legs 64 at one end of each assembly 12 is provided with a depending skirt 68 which terminates in a frustoconical lip as previously described for the skirts 56 and 58, and an upstanding threaded stud 70 which extends along the longitudinal axis of the spacer unit 22. A layer of the bonding agent 54 joins the skirt 68 to the cap 46 of the insulator 14. The conductor clamp 63 presents a U-shaped yoke 72 which pivotally receives a saddle clamp 74 by means of a nut and bolt assembly 76. The saddle clamp 64, in turn, holds a conductor cable 78. The yoke 72 has an opening in its horizontal crossarm which permits the clamps 63 to be positioned over the stud 70- and held in place by a nut and washer assembly 80. It is to benoted that each connecting leg 66 at the other end of each assembly 12, in place of a skirt such as 68, is provided with a tongue 82 (only partially visible in FIG. 1) of the same configuration as the tongue 60 previously described. The connecting leg 66 is also provided with a threaded stud 83 which receives a clamp 63 in the same manner as connecting leg 64. A second nut and washer assembly secures the clamp 63 to the connecting leg 66, and a second saddle clamp 74 receives a second conductor 85 in the same manner as previously described for the conductor 78.

As illustrated in FIG. 3, the connecting legs 64 and 66 can also accommodate conductor clamps 63a, each of which is provided with a threaded bore 84 thus permitting a clamp 63a to be received directly by a threaded stud 70 without the need for auxiliary fastening means such as the nut and washer assembly 80. 1 I

While no protective jacket is shown in FIGS. 1 and 3 surrounding the spacer unit 22, it is to be understood that a jacket such as 36 could be utilized with the alternative embodiment 62 or a protective coating applied to the unit 22 to increase the life thereof. An appropriate parting agent such as described above in connection with the apparatus 10 is placed on the metal surfaces of the metal surfaces of the apparatus 62 with which the bonding agent 54 comes in contact. It will be appreciated that the alternative embodiment 62 has the same high compressive strength and flashover resistance characteristics as the apparatus 10, and by using the connecting legs 64 and 66 to join the conductor clamps to the insulators 14 and 16, a single type of conductor clamp may be utilized at either end of the apparatus.

Referring to FIG. 4 of the drawings wherein a third alternative embodiment of the midspan spacer is designated generally by the numeral 86, it is seen that the apparatus 86 utilizes an insulator assembly 87 which includes an elongated, relatively lightweight spacer unit 22 of the type previously described, and a pair of insulators 88 at either end of the spacer unit 22 having multiple insulator skirts 90 which are preferably cast from resinous material about a central rod 92. Each of the insulators 88 has a pair of opposed, frustoconical end portions 94 and 96 which project from the endmost insulator skirts 90. A pair of conductor clamps 98, each of which is provided with a depending leg portion 100- having an opening therein is secured to the outwardly projecting end portion 94 by a suitable bonding agent 101. The other projecting end portions 96, one of which is visible in FIG. 4, are each received in ferrules 102 and 103 and secured thereto by a layer of the bonding material 101. Each of the ferrules 102 and 103 also receives one end of the spacer unit 22, the latter also being secured by a suitable bonding agent (not shown). An appropriate parting agent is used in connection with the bonding layers for reasons previously discussed.

It will be appreciated that the multiple insulator skirts 90 which are an integral part of the apparatus 86 give the apparatus superior flashover resistance characteristics, thereby making this embodiment particularly useful where atmospheric or electrical conditions warrant increased insulative properties. Production advantages are also inherent in an insulator such as 88 which can be cast from a resinous material.

Referring to FIG. 5 wherein a fourth alternative embodiment 104 is illustrated, the apparatus 104 employs an elongated insulator assembly 106 which includes an elongated spacer unit 107 constructed from the same lightweight insulative material as the spacer unit 22 previously described, and a pair of insulators 108 secured to either end thereof. Each of the insulators 108 is provided with frustoconical end projections 110 and 112 which extend from a central rod 114 around which the insulator skirt 116 is cast preferably from a resinous material. A pair of conductor clamps 118, each of which has a depending leg portion 120, are secured to the end projections 110 and 112 respectively by a layer of the bonding agent 101 in the same manner as previously described for the conductor clamps 98. Each of the other end projections 110 and 112 is disposed within a connecting ferrule 122 and held therein by a layer of the bonding agent 101. Again, an appropriate parting agent is utilized in connection with the bonding agent 101. It is to be noted that the spacer unit 107 differs from the spacer units 22 previously described in that it is provided with frustoconical end projections 124 and 126 which are received by the connecting ferrules 122 and held therein by a layer of the bonding agent 101. A protective jacket 36 of the type previously described, surrounds the spacer unit 107 and abuts the connecting ferrules 122.

Referring to FIG. 6 wherein the last alternative embodiment of the invention is shown, the apparatus 128 includes an elongated insulator assembly 130 having an elongated spacer unit 132 constructed from a fiberglass reinforced resinous material and a pair of insulators 134 disposed at either end of the unit 132. The spacer unit 132 is characterized by double frustoconical end projections 136 and 138. Similarly, each insulator 134 comprises a central rod 140 around which an insulator skirt 142 is cast, preferably from a resinous material having high flashover resistance characteristics, and the ends of each of the rods 140 extend outwardly from the skirt 142 to present double frustoconical end portions 144 and 146. A pair of conductor clamps 148, each having a depending leg portion 150 with an opening therein which defines a double frustoconical socket, receive the outwardly extending frustoconical end portions 144 and 146 respectively of the two insulators 134 and the same are secured thereto by a layer of the bonding agent 101. The inwardly projecting end portions 144 and 146 of the two insulators 134 are received within a double frustoconical socket of a pair of connecting ferrules 152 and 154 and also secured by the bonding agent 101. It is to be understood, of course, that an appropriate parting agent is used with the bonding agent 101, as previously discussed. A second double frustoconical socket in each of the connecting ferrules 152 and 154 receives the double frustoconical end projections 136 and 138 respectively with the bonding agent 101 again completing the connection. A protective jacket 36 of the type previously described surrounds the spacer unit 132 and abuts the connecting ferrules 152 and 154.

It is to be noted that the spacer units 107 and 132 are distinguishable from the spacer units 22 previously described by their frustoconical end portions which are received within the respective connecting ferrules. This arrangement serves to transfer tensile loads to compression loads on the bonding agent 101 and is particularly advantageous where excessive strains are exerted on the insulator assembly. The spacer unit 132 differs from the unit 107 only in that it is provided with double frustoconical end portions as are the adjoining insulators 134. This arrangement would normally be used only when extremely high forces tending to move the two conductors held by the spacer away from each other are likely to be encountered. It is to be understood, of course, that in those instances where relatively small forces are encountered tending to move the two conductors held by a spacer away from each other the frustoconical compression fittings shown on any of the foregoing embodiments could be omitted and a noncompression fitting substituted therefor. Furthermore, with any of the embodiments shown and described herein, the spacer units 22, 107 and 130 can be constructed in varying lengths to accommodate different spacing between conductors of a multiple phase transmission line. While various forms of insulators have been shown in the foregoing embodiments, other forms of insulators could be used without departing from the scope of the invention. For example, an insulator string of any length necessary to provide the required flashover resistance characteristics, could be substituted for any of the insulators shown and described herein,

It will be appreciated that with any of the embodiments shown an described a rigid spacer assembly is presented wherein the component parts can be effectively tightened to minimize radio interference. Such a rigid assembly will preclude torsional movements of the spaced conductors and is, therefore, extremely effective in controlling galloping conductors yet, because of its light weight, does not adversely affect the drape of the lines.

While damage to transmission line hardware is common from such sources as lightning, current surges, and hunters, it

is readily apparent that with any of the spacer embodiments shown and described the various component parts can be individually replaced without replacement of the entire spacer assembly.

Having thus described the invention, what I claim as new and desired to be secured by Letters Patent is:

l. A midspan spacer for maintaining adjacent high voltage conductors in normal predetermined spaced relationship, said spacer comprising:

a clamp for each conductor;

yoke structure supporting each conductor clamp for pivoting movement thereof only about an axis extending transversely of a respective conductor; and

an elongated insulator assembly rigidly affixed to and maintaining said yoke structures and the conductor clamps carried thereby in spaced relationship, said assembly being of a length to substantially span the normal distance between said conductors and thereby maintain the latter in said predetermined spaced relationship,

said assembly including an elongated, relatively lightweight spacer unit of insulating material and having a high compressive strength in relationship to the weight thereof to prevent flow of current between the conductors held by said clamps and to prevent movement of said conductors toward and away from each other under widely varying loads and operating conditions, and

at least one insulator having high flashover characteristics rigidly interposed between each extremity of the unit and a corresponding yoke structure.

2. Apparatus as set forth in claim 1, including a bonding agent joining said insulators to respective yoke structures; and frustoconical bond-engaging means for loading said agent in compression when said conductors tend to move relative to one another.

3. Apparatus as set forth in claim 2, each of said yoke structures having an elongated opening therein, said bonding agent being disposed within said openings, said bond-engaging means comprising a tongue rigid with each of said insulators disposed within an adjacent opening.

4. Apparatus as set forth in claim 2, wherein each of said insulators is configured to present a cap on one side thereof and a cavity on theother side thereof, one of said insulators being disposed with its cap extending toward said assembly, the other of said insulators being disposed with its cap extending away from said assembly, said bonding agent being disposed within the cavity of said one insulator and around the cap of said other insulator, said bond-engaging means including a leg depending from one of said yoke structures and disposed within the cavity of said one insulator and a skirt depending from the other of said yoke structures and disposed in circumscribing relationship to the cap of said one insulator and the bonding agent thereon. v

5. Apparatus as set forth in claim 4, said assembly including a first connecting portion configurated to receive the cap of said one insulator and a second connecting portion configurated to be received within said cavity in the other insulator.

6. Apparatus as set forth in claim 5, including a bonding agent joining said portions to said insulators, each of said portions including frustoconical bond-engaging means for loading said agent in compression when said conductors tend to move relative to one another.

7. Apparatus as set forth in claim 6, said assembly including a pair of connecting ferrules each having opposed openings therein, one of said openings receiving one end of a respective connecting portion; and an elongated insulating rod having its end disposed in the other of said openings.

8. Apparatus as set forth in claim 7, and a jacket of insulating material surrounding said rod and in frictional engagement therewith, said jacket abutting the respective connecting ferrules.

9. Apparatus as set forth in claim 1, said insulator comprising an annular porcelain body having an uninterrupted curvilinear first surface and a second surface comprising a plurality of interconnected annular ridges.

10. A midspan spacer for maintaining adjacent high voltage a connecting clamp for each conductor, each of said clamps having a conductor receiving saddle and yoke structure pivotally supporting the saddle for pivoting movement thereof only above an axis extending transversely of a respective conductor, each of said yoke structure having a depending leg portion with an opening therein;

an insulator for each clamp respectively and having relatively high flashover resistance characteristics, each of said' insulators having a projecting end portion, said end portion of each insulator being received within a respective opening;

first connecting means rigidly securing said end portion of each insulator to a corresponding yoke structure within a respective opening;

an elongated, relatively lightweight unit of insulating material of a length to substantially span the distance between said conductors, said unit having a relatively high compressive strength in relationship to the weight thereof; and

second connecting means rigidly joining the corresponding ends of said unit to respective insulators for maintaining said conductors in predetermined spaced relationship.

11. Apparatus as set forth in claim 10, wherein said first connecting means comprises a bonding agent within each of said openings and each of said end portions is of a frustoconical configuration to thereby load said bonding agent in compression when said conductors tend to move relative to one another.

12. Apparatus as set forth in claim 10, each of said insulators having a second projecting end portion in opposed relationship to the first mentioned projecting end portion, said second connecting means comprising a pair of connecting ferrules each having opposed openings therein, one of said openings receiving said second projecting end portion of a respective insulator, the other of said openings receiving the respective ends of the insulating unit.

13. Apparatus as set forth in claim 10, wherein each of said insulators comprises an elongated rod of resinous insulating material with a resinous insulating skirt secured to said rod intermediate the ends thereof.

14. Apparatus as set forth in claim 13, wherein a plurality of insulator skirts are disposed, in closely spaced relationship intermediate the ends of said rod. 

1. A midspan spacer for maintaining adjacent high voltage conductors in normal predetermined spaced relationship, said spacer comprising: a clamp for each conductor; yoke structure supporting each conductor clamp for pivoting movement thereof only about an axis extending transversely of a respective conductor; and an elongated insulator assembly rigidly affixed to and maintaining said yoke structures and the conductor clamps carried thereby in spaced relationship, said assembly being of a length to substantially span the normal distance between said conductors and thereby maintain the latter in said predetermined spaced relationship, said assembly including an elongated, relatively lightweight spacer unit of insulating material and having a high compressive strength in relationship to the weight thereof to prevent flow of current between the conductors held by said clamps and to prevent movement of said conductors toward and away from each other under widely varying loads and operating conditions, and at least one insulator having high flashover characteristics rigidly interposed between each extremity of the unit and a corresponding yoke structure.
 2. Apparatus as set forth in claim 1, including a bonding agent joining said insulators to respective yoke structures; and frustoconical bond-engaging means for loading said agent in compression when said conductors tend to move relative to one another.
 3. Apparatus as set forth in claim 2, each of said yoke structures having an elongated opening therein, said bonding agent being disposed within said openings, said bond-engaging means comprising a tongue rigid with each of said insulators disposed within an adjacent opening.
 4. Apparatus as set forth in claim 2, wherein each of said insulators is configured to present a cap on one side thereof and a cavity on the other side thereof, one of said insulators being disposed with its cap extending toward said assembly, the other of said insulators being disposed with its cap extending away from said assembly, said bonding agent being disposed within the cavity of said one insulator and around the cap of said other insulator, said bond-engaging means including a leg depending from one of said yoke structures and disposed within the cavity of said one insulator and a skirt depending from the other of said yoke structures and disposed in circumscribing relationship to the cap of said one insulator and the bonding agent thereon.
 5. Apparatus as set forth in claim 4, said assembly including a first connecting portion configurated to receive the cap of said one insulator and a second connecting portion configurated to be received within said cavity in the other insulator.
 6. Apparatus as set forth in claim 5, including a bonding agent joining said portions to said insulators, each of said portions including frustoconical bond-engaging means for loading said agent in compression when said conductors tend to move relative to one another.
 7. Apparatus as set forth in claim 6, said assembly including a pair of connecting ferrules each having opposed openings therein, one of said openings receiving one end of a respective connecting portion; and an elongated insulating rod having its end disposed in the other of said openings.
 8. Apparatus as set forth in claim 7, and a jacket of insulating material surrounding said rod and in frictional engagement therewith, said jacket abutting the respective connecting ferrules.
 9. Apparatus as set forth in claim 1, said insulator comprising an annular porcelain body having an uninterrupted curvilinear first surface and a second surface comprising a plurality of interconnected annular ridges.
 10. A midspan spacer for maintaining adjacent high voltage conductors in normal predetermined spaced relationship, said spacer comprising: a connecting clamp for each conductor, each of said clamps having a conductor receiving saddle and yoke structure pivotally supporting the saddle for pivoting movement thereof only above an axis extending transversely of a respective conductor, each of said yoke structure having a depending leg portion with an opening therein; an insulator for each clamp respectively and having relatively high flashover resistance characteristics, each of said insulators having a projecting end portion, said end portion of each insulator being received within a respective opening; first connecting means rigidly securing said end portion of each insulator to a corresponding yoke structure within a respective opening; an elongated, relatively lightweight unit of insulating material of a length to substantially span the distance between said conductors, said unit having a relatively high compressive strength in relationship to the weight thereof; and second connecting means rigidly joining the corresponding ends of said unit to respective insulators for maintaining said conductors in predetermined spaced relationship.
 11. Apparatus as set forth in claim 10, wherein said first connecting means comprises a bonding agent within each of said openings and each of said end portions is of a frustoconical configuration to thereby load said bonding agent in compression when said conductors tend to move relative to one anotheR.
 12. Apparatus as set forth in claim 10, each of said insulators having a second projecting end portion in opposed relationship to the first mentioned projecting end portion, said second connecting means comprising a pair of connecting ferrules each having opposed openings therein, one of said openings receiving said second projecting end portion of a respective insulator, the other of said openings receiving the respective ends of the insulating unit.
 13. Apparatus as set forth in claim 10, wherein each of said insulators comprises an elongated rod of resinous insulating material with a resinous insulating skirt secured to said rod intermediate the ends thereof.
 14. Apparatus as set forth in claim 13, wherein a plurality of insulator skirts are disposed in closely spaced relationship intermediate the ends of said rod. 